Centrifuge systems for continuously removing liquid from metal chips or other material impregnated with lubricating or other fluids are known. Such a system is illustrated, for example, in U.S. Pat. No. 4,936,822 issued to William D. Nemedi. In the particular system disclosed in this patent, a centrifugal separator bowl is preferably cast with a plurality of recesses disposed in the internal vertical and bottom walls of a rotatable bowl. A plurality of blade assemblies are disposed in the various recesses, each blade assembly comprising a pad having a structural configuration of a bowl recess. A blade extends outwardly from a pad, the blade being connected to the pad along both the bottom blade edge and a substantial portion of the outer vertical blade edge. When a wear spot occurs at the intersection of a blade and pad, the blade-pad assembly is relatively readily and easily removed from a bowl recess and another blade-pad assembly can be releasably fastened in the vacated bowl recess.
While bowl wear has been reduced by the utilization of replaceable bowl/blade assemblies, a material wear problem sometimes exists with respect to the centrifugal separator. In a centrifugal separator, a porous screen which serves to pass lubricant therethrough, is fastened to the top of the separator bowl. The screen is fixed relative to the bowl and blades and rotates with the bowl and blades. One type of a porous screen is referred to as a profile screen. A profile screen includes a plurality of fingers each of which comprises an elongated relatively thin tapered bar. The fingers are spaced closely to one another in a ring-like fashion and are held together by ring plates. The fingers form a plurality of narrow tapered openings or slots having a slot thickness adjacent the front surface of the screen of approximately 0.02 inches. The screen opening is tapered outwardly so that each of the slot openings is slightly enlarged at the back surface of the screen.
When a centrifugal separator is in operation, material such as metal chips is centrifuged in the rotating bowl. As the material is centrifuged, it travels upward along the vertically inclined bowl wall and passes onto the profile screen at which location entrained lubricant or other fluid separates from the chips and passes through the narrow screen openings. The relatively dry metal chips or other solid material continue to move upward passing over the screen into a discharge chamber from which the chips exit the separator and pass to a collection site.
It has been found that, in some instances, as the chip and lubricant material travel upwardly along the inclined vertical separator bowl wall onto the profile screen, substantial areas of wear are generated both on the front or inner surface of the profile screen as well as on the separator bowl wall in areas immediately below the screen wear areas. It has been found that in various applications, excessive wear will occur at one or more locations on the screen and bowl. Areas of excessive screen wear serve to cause the relatively narrow openings or slots at the front surface of the screen to enlarge whereby metal chips or other undesired solid materials pass through the screen openings. Chips which pass through the screen openings with the fluid follow the fluid recirculation path, the adverse effect of which is that the chips can plug or otherwise damage a recirculating pump or the like in the fluid recirculation system. Further, chips which mix with the fluids which are passing through the screen openings must be collected and reprocessed through the centrifugal separator to separate the fluid from the chips, i.e., dry the metal chips or material.
It also has been found that excessive screen wear occurs predominantly at the location where the screen is positioned contiguous to one or more blades located within and attached to the rotatable separator bowl. Material to be separated travels upwardly along the inclined bowl wall and particularly at the location of the intersection of the leading edge of a blade in the direction of rotation and the bowl wall. As the material reaches the top of the bowl wall, it contacts the screen member and primarily the screen surface areas contiguous to the blades seated in the bowl. Over a period of time, excessive screen wear occurs at the areas of the screen surface positioned above and proximate to the blades. The effect is that screen wear is not uniform about the screen but rather screen wear will occur at a faster rate at different locations on the screen.
What is desired is to preclude metal chips or other undesired solid materials from passing through screen openings which have been enlarged due to screen wear. It is also desired to avoid excessive screen wear by extending the life of a screen which is a relatively costly component in a centrifugal separator device.